Multi-colored liquid crystal display device

Abstract

A liquid crystal display device capable of displaying multiple colors in response to application of different driving voltages includes a liquid crystal cell with two polarizers and the value of the product of the optical anisotropy n of the nematic liquid crystal material and the thickness d of the liquid crystal layer is in excess of 1.1 μm. A second liquid crystal cell can be included between the first cell and one of the polarizers. A driver circuit drives the liquid crystal cells by the dynamic drive method by applying a selecting voltage, a non-selecting voltage, and one or more intermediate voltages to generate the different colors.

What is claimed is: 
     
       1. An electrooptical display device which displays different colors when driven with different driving voltages, comprising: a liquid crystal cell including a pair of opposed substrates having electrodes selectively disposed thereon, the substrates spaced apart distance d and a twisted nematic liquid crystal material between the substrates;   each substrate having an orientation direction for aligning liquid crystal molecules adjacent the substrates to be substantially parallel with the orientation direction;   the cell formed so that the value of the product of the optical anisotropy n of the liquid crystal material and the thickness d of the liquid crystal layer is in excess of about 1.1 μm;   a pair of polarizers disposed on the exterior sides of the liquid crystal cell; and   circuit means for selectively generating voltage having at least three different values for displaying multiple colors coupled to the electrodes on the substrates.   
     
     
       2. The electrooptical display device of claim 1, wherein the twist angle of the liquid crystal material is in the range of about 180° to 360°. 
     
     
       3. The electrooptical display device of claim 2, wherein the circuit means is a dynamic driving circuit capable of applying, to the electrodes, a selecting voltage, a non-selecting voltage and at least one intermediate voltage. 
     
     
       4. The electrooptical display device of claim 3, wherein the directions of the axes of polarization of the polarizers are shifted from the orientation directions of the liquid crystal molecules adjacent to the substrate adjacent to the polarizer by 15° to 75°. 
     
     
       5. The electrooptical display device of claim 2, wherein the directions of the axes of polarization of the polarizers are shifted from the orientation directions of the liquid crystal molecules adjacent to the substrate adjacent to the polarizer by 15° to 75°. 
     
     
       6. The electrooptical display device of claim 2, wherein the optical anisotropy of the liquid crystal material is between about 0.1 and 0.25. 
     
     
       7. The electrooptical display device of claim 2, wherein the optical anisotropy of the liquid crystal material is between about 0.13 and 0.22. 
     
     
       8. The electrooptical display device of claim 2, wherein the liquid crystal layer is between about 5 and 12 μm thick. 
     
     
       9. The electrooptical display device of claim 2, wherein the value of the product  n·d is less than about 2.5. 
     
     
       10. The electrooptical display device of claim 1, wherein the at least three voltage values cause the device to display at least three of the colors red, green, yellow and blue, each different color corresponding to a different respective voltage. 
     
     
       11. The electrooptical display device of claim 10, wherein one of the voltages corresponds to the color red and another of the voltages corresponds to the color blue. 
     
     
       12. A method of providing a color display, comprising: applying a voltage to a liquid crystal display cell, the voltage including a selecting voltage, a non-selecting voltage and at least one intermediate voltage;   the liquid crystal cell including a pair of opposed substrates having electrodes disposed thereon, the substrate spaced apart a distance d and a liquid crystal material between the substrates, the liquid crystal cell formed so that the value of the product of the optical anisotropy  n of the liquid crystal material and the thickness d of the liquid crystal layer being greater than about 1.1 μm and a pair of polarizers are disposed on the exterior sides of the liquid crystal cell.   
     
     
       13. The method of claim 12, wherein the twist angle of the liquid material is in the range of between about 180° to 360°. 
     
     
       14. The method of claim 13, including applying at least three intermediate voltages between the selecting voltage and non-selecting voltage. 
     
     
       15. The method of claim 13, wherein the liquid crystal cell is driven by a dynamic drive and displays multiple colors at a duty ratio below about 1/100. 
     
     
       16. A liquid crystal display device which displays different colors when driven with different driving voltages, comprising: a liquid crystal cell including a pair of opposed substrates having electrodes selectively disposed thereon and a nematic liquid crystal material having a twist angle between about 180° and 360° within the cell and circuit means coupled to the electrodes for selectively generating voltages having at least three different values to be applied to the cell including a first voltage, a second voltage and a third voltage to cause the cell to display at least three different colors including a first, a second and a third different color, corresponding to the first, second and third voltages, respectively.   
     
     
       17. The liquid crystal display device of claim 16, wherein the first, second and third colors are at least three of the colors red, green, yellow and blue, respectively. 
     
     
       18. The liquid crystal display device of claim 17, wherein the first color is red, the second color is green and the third color is blue. 
     
     
       19. The liquid crystal display device of claim 16, wherein the first color is red and the second color is blue.